The metal that is used in molten form to join pieces of metal. Various solders are produced commercially for different types of soldering, having different melting points for 'hard soldering' and'soft soldering'.The solder for gold and silver must have the same proportions of the precious metal as the pieces to be joined, and such solders are now made by refiners with the prescribed proportions. Solders thatmelt readily are 'soft solders'; those that fuse only at red heat are 'hard solders'.